It has until now been difficult to create images particularly for infrared cameras, which have a wide dynamic range, for example ranging from −5° C. to 1100° C., and to maintain a very good sensitivity across the whole temperature range, and particularly for the lower signal levels.
It is a well known disadvantage in relation to pure IR images that the users often have some difficulty to interpret the view that is shown. IR images are often more blurred than visual images because the wavelength region from the illustrated scene is different and the transitions between different temperatures are rather smooth. It is to be noted that an IR image is essentially based on different intensity of the shown objects within practically the same wavelength region, and the image is thus not very dependent on the wavelength, unlike images based on the visible wavelength region. Higher temperature at an object gives in principle a higher intensity. The different shades of intensity are given in a chosen colour scale, for example a high intensity is shown in red and a low brightness is shown in blue or violet.
A problem to solve is to make temperatures in a wide dynamic temperature range clear, distinct, and with good resolution even for the lower signal levels.
The invention has been particularly developed for use in IR cameras. However, it could also be used in any other kind of imaging device. One example of such a device is in infrared imagers for fire fighters. In such an imager a line scanning is made from an air borne vehicle flying over the object, which can be a forest. A demand on such systems is that they shall be able to present images with good resolution and accuracy both for room temperature and high temperature scenes simultaneously.